Waste products are either buried, stored, purified or salvaged. Sewer sludge is usually aerated to reduce the biological oxygen demand (BOD) and then runoff into a large body of water. Occasionally, its dilute form is salvaged for irrigation purposes. However, it is also possible to utilize the sewerage sludge as the bloating agent in the manufacture of expanded shale aggregates by mixing digested sewerage sludge with shale and burning the mix in a vertical kiln or rotary kiln at 2000.degree. C. It is also possible to lower the melting point of shale by mixing high-lime blast furnace slag as the fluxing agent. Furthermore, the high-lime blast furnace slag can also be used to control the sulfur dioxide emission of the kiln. The sulfur and other acidic gases formed in the burning of the shale, dewatered digested sewerage sludge and refuse derived fuel reacts with the calcium oxide present in the high-lime blast furnace slag forming solid calcium sulfate and other calcium salts which are retained in the expanded shale aggregate, thereby reducing the acidic pollutants emitted into the atmosphere. If the light-weight expanded shale aggregates produced in this manner uses dewatered digested sewerage sludge, high-lime blast furnace slag and refuse derived fuel to fire the kiln which are all waste products, a new useful composition is produced from these three waste ingredients. An important unanticipated result in using the three waste products namely, dewatered digested sewerage sludge, high-lime blast furnace slag and refuse derived fuel products complimentary characteristic wherein the burning of refuse derived fuel at 2000.degree. C. deodorizes the refuse derived fuel and the dewatered digested sewerage sludge and also the acidic emission produced in the burning of refuse derived fuel and the digested dewatered sewerage sludge reacts with the calcium oxide in the high-lime blast furnace slag thereby neutralizing the acid and retaining reaction products in the expanded shale aggregates resulting in the reduction of air pollution.